(1) Field of the Invention
The present invention relates to a jumper assembly for tension insulator strings, and more particularly to shielding by jumper assembly for preventing corona discharge occurring on the energized side of tension insulator strings mainly for extra-high voltage overhead transmission lines.
(2) Description of the Prior Art
Recently, as the capacity of the electric power transmission has generally been greatly increased, the insulator assemblies for high voltage transmission have become large in size. In general, these insulator assemblies have shield rings for preventing corona discharge or arcing horns for protecting insulators from power arc and preventing corona discharge. With such large-sized insulator assemblies and particularly tension insulator strings, large-sized shield rings must be provided for preventing corona discharge from the insulator strings because of the reduced shielding effect of the conductors. Such a large shield ring, however, has a disadvantage in that the corona characteristics of the shield ring itself become degraded contrary to what is expected due to corona discharge from water droplets on the shield ring under wet conditions.
To overcome this disadvantage, it has been suggested that the shield ring be made as a multiple shape in the form of a cage having a large outer diameter. However, a shield ring of this type is not practical because it is difficult to install, expensive to manufacture, and is likely to be covered with snow.